Steven Hunter

Mitral repair best practice: proposed standards

Objectives: To define best practice standards for mitral valve repair surgery. Design: Development of standards for process and outcome by consensus. Setting: Multidisciplinary panel of surgeons, anaesthetists, and cardiologists with interests and expertise in caring for patients with severe mitral regurgitation. Main outcome measures: Standards for best practice were defined including the full spectrum of multidisciplinary aspects of care. Results: 19 criteria for best practice were defined including recommendations on surgical training, intraoperative transoesophageal echocardiography, surgery for atrial fibrillation, audit, and cardiology and imaging issues. Conclusions: Standards for best practice in mitral valve repair were defined by multidisciplinary consensus. This study gives centres undertaking mitral valve repair an opportunity to benchmark their care against agreed standards that are challenging but achievable. Working towards these standards should act as a stimulus towards improvements in care.

Release of platelet-derived growth factor activity from pig venous arterial grafts.

Intimal smooth muscle cell proliferation and superimposed atheroma are the main causes of late failure of saphenous vein bypass grafts. It has been suggested that these reactions are caused by the production of growth factors from the cells of the vessel wall. To test this hypothesis, we cultured segments of pig venous arterial grafts, removed 1 and 4 weeks after implantation, in serum-free medium for 24 hours. Tissue viability as assessed by adenosine triphosphate concentration was maintained throughout the 24-hour culture period (239 +/- 21 nmol/gm wet weight [standard error of the mean], n = 26, 0 hours; 240 +/- 24 nmol/gm wet weight, n = 17, 24 hours). Cell proliferation occurred and autoradiography showed proliferating cells to be located in the neointimal and medial layers. These cells were identified as smooth muscle cells by means of a monoclonal antibody to alpha-actin. Graft-conditioned media were tested for mitogenic activity by means of a fibroblast proliferation assay. Media conditioned for 24 hours produced significant stimulation of cell growth (284% +/- 30%, n = 17) above that obtained in culture medium alone (100%). This mitogenic activity was inhibited by 61% +/- 9%, n = 8, with a polyclonal-neutralizing antibody to platelet-derived growth factor. Reverse-transcription polymerase chain reaction analysis and Northern blots demonstrated platelet-derived growth factor B messenger ribonucleic acid (mRNA) in vein grafts but not in ungrafted vein. Analysis of graft tissue sections by in situ hybridization demonstrated an abundance of platelet-derived growth factor B mRNA positive cells in the endothelial and neointimal layers, as well as in the endothelial cells of the adventitial vessels. These data constitute direct evidence for active growth factor production within the cells of the vein graft. They also suggest that endogenously produced platelet-derived growth factor may play a role in regulating smooth muscle cell proliferation in this model.

Should Thyroid Function Be Assessed Before Cardiopulmonary Bypass Operations

Thyroid function is depressed during and after cardiopulmonary bypass surgical procedures, and this may adversely affect myocardial performance. There is known to be a high prevalence of thyroid abnormalities in the elderly population, and many patients undergoing cardiac operations fall into this category. We have assessed thyroid function in 116 patients admitted for elective open heart procedures to determine the value of preoperative testing. Abnormalities in thyroid function were present in 13 (11.2%) of the patients studied, 3 of whom were receiving thyroxine therapy. One patient who had overt hypothyroidism died postoperatively of a large cerebral infarct; 11 had elevated thyrotropin levels with normal serum thyroxine levels; and 1 who had overtreated hypothyroidism suffered fast atrial fibrillation postoperatively. No other complications were observed. These findings indicate that thyroid function should be assessed preoperatively in patients already on thyroxine therapy. Whether thyroid function should be evaluated routinely in all patients before operations involving cardiopulmonary bypass is not clear. Although there is a high incidence of abnormal laboratory results, there were no apparent adverse effects on the surgical outcome.

Adverse hemodynamic effects of pericardial closure soon after open heart operation

The short-term hemodynamic effects of pericardial closure on cardiac function were studied during steady-state anesthesia and ventilation in 10 patients (6 men) (mean age, 59 +/- 9 years) who underwent an open-heart valve operation. Observations were made after the heart was decannulated, both while the pericardium was open and after it had been closed, and then after closure of the chest after the pericardium had been reopened by removing the pericardial suture through the chest wall. The effect of closing the pericardium before closing the chest was an immediate reduction in cardiac output (thermodilution) of 1.39 +/- 0.24 L/min from 5.09 +/- 0.40 L/min (p less than 0.001). The heart rate remained stable, but there was a decrease in stroke volume of 29% and an increase in systemic vascular resistance of 34% (both, p less than 0.01). The mean arterial pressure increased slightly by 2% (not significant). Opening the pericardium (1.5 to 2 hours after the end of the operation) while the chest remained closed was followed by an increase in cardiac output of 1.33 +/- 0.15 L/min from 4.12 +/- 0.62 L/min (p less than 0.001). As the heart rate and the mean blood pressure changed insignificantly, there was an increase in stroke volume of 15 +/- 3 mL from 53 +/- 5 mL and a reduction in systemic vascular resistance of 473 +/- 83 dyne . s . cm-5 from 1,721 +/- 181 dyne.s.cm-5 (both, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Is a port-access mitral valve repair superior to the sternotomy approach in accelerating postoperative recovery?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether port-access mitral valve repair reduces the recovery period of patients compared to the conventional sternotomy approach. Using the reported search, 778 papers were identified. Thirteen papers represented the best evidence on the subject and the author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results and study comments and weaknesses were tabulated. The 13 papers demonstrated that patients who undergo minimally invasive mitral valve repair have a shorter ICU and total hospital stay than those who undergo the sternotomy approach. Results vary but mean hospital stays range from 5.6 to 13 days in port-access groups compared to 6.25-15 days in sternotomy groups. Other advantages over the sternotomy approach were reduced postoperative bleeding and pain, shorter time to extubation and a quicker return to daily activities. However, it is consistently reported that operative time is longer, with the increase in bypass time being around 30 min. We conclude that in several cohort studies minimally invasive mitral valve repair is reported to result in a shorter ICU and hospital stay, reduced postoperative bleeding and pain and a shorter time to resuming normal activities. This is at the expense of longer bypass and operative times.

A surgical technique that preserves human saphenous vein functional integrity

We investigated the effect of a novel surgical preparative technique for human saphenous vein by using the concentration of adenosine triphosphate and the adenosine triphosphate/diphosphate ratio to quantify medial integrity and by using stimulated rates of prostacyclin production to quantify endothelial function. Freshly isolated vein had an adenosine triphosphate concentration of 358 +/- 54 nmol.g-1 wet weight and an adenosine triphosphate/diphosphate ratio of 2.89 +/- 0.13 (n = 12); it produced prostacyclin in response to fluid shear at a rate of 14.3 +/- 2.0 pg.min-1.mg-1 wet weight (n = 12). Surgically prepared vein obtained on completion of the last proximal anastomosis had been distended with the patients own arterial pressure using a side-arm connected to the aortic cannula. This vein had an adenosine triphosphate concentration of 413 +/- 70 nmol.g-1 wet weight and an adenosine triphosphate/diphosphate ratio of 2.74 +/- 0.44 (n = 11), and it produced prostacyclin at a rate of 13.1 +/- 0.2 pg.min-1.mg-1 wet weight (n = 12). All values were indistinguishable from those in freshly isolated vein. The results demonstrate that this simple technique for distention at arterial pressure preserved medial and endothelial function.

Endoaortic Clamping Does Not Increase the Risk of Stroke in Minimal Access Mitral Valve Surgery: A Multicenter Experience

BACKGROUND Some controversy exists regarding the safety of endoaortic balloon clamping in minimal access isolated mitral valve surgery (MIMVS). The aim of this European multicenter study was to analyze the results in 10 experienced centers and compare the outcomes with published data. METHODS The most recent 50 consecutive MIMVS cases from 10 European surgeons who had performed at least 100 procedures were prospectively collected and retrospectively analyzed. All procedures were performed through right minithoracotomy with femoral cannulation and endoaortic balloon occlusion. In-hospital and 30-day outcomes were studied. Mortality and stroke rates were compared with published median sternotomy and MIMVS outcomes. RESULTS Mean age was 63.2 ± 12.5 years, 289 (57.8%) were male, mean logistic European system for cardiac operative risk evaluation was 6.1 ± 6.2, and 53 (10.6%) procedures had cardiac reoperations. Concomitant procedures were performed in 126 (25.9%) cases. Three patients (0.6%) required conversion to full sternotomy. Ten patients (2.0%) necessitated endoaortic balloon clamping conversion (8 to external clamping), and re-exploration for bleeding was necessary in 24 (4.8%) cases. Mean aortic cross-clamp and cardiopulmonary bypass times were 85.6 ± 30.1 and 129.5 ± 40.2 min, respectively, and were significantly longer for concomitant procedures (p < 0.001). There were no aortic dissections and no deep venous thromboses. Operative mortality (none neurologic) and major stroke occurred in 7 (1.4%) and 4 (0.8%) patients, respectively. These rates compared favorably with the published literature on isolated primary mitral valve surgery (MVS) through sternotomy or minithoracotomy (mortality rates 0.2% to 11.6%, stroke rates 0.6% to 4.4%). CONCLUSIONS Once procedural proficiency is acquired, endoaortic balloon clamping in MIMVS is a safe and effective technique. Despite the fact that this patient cohort also includes combined and redo procedures, the observed mortality and stroke rate compared favorably with the existing literature on primary isolated mitral valve surgery irrespective of the approach.

Is steroid therapy ever of benefit to patients in the intensive care unit going into septic shock

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was, is steroid therapy ever of benefit to patients in the intensive care unit going into septic shock? Using the reported search 1505 papers were identified. Fourteen papers represented the best evidence on the subject. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results and study comments and weaknesses were tabulated. Recent guidelines from the Surviving Sepsis Campaign recommend using stress doses of corticosteroids for septic shock regardless of adrenal function. All patients undergoing cardiothoracic surgery are at risk of developing septic shock. The 14 papers demonstrated that 28-day mortality is unaffected by hydrocortisone, however, the time to shock reversal is significantly reduced. Steroids reduced inflammatory mediators (IL-6, IL-8 and CRP) and neutrophil activation whilst maintaining neutrophil phagocytic functions. Haemodynamically, they increased systemic vascular resistance (SVR) and mean arterial pressure (MAP) and reduced heart rate (HR) and glomerular permeability. We conclude that steroids have no effect on mortality but shorten time to shock reversal, therefore they have a limited capacity in septic shock patients. Their immunological and haemodynamic effects cannot be discounted and could benefit patients in severe septic shock with adrenal insufficiency.

Does biventricular pacing provide a superior cardiac output compared to univentricular pacing wires after cardiac surgery

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether biventricular pacing provides a superior cardiac output compared to univentricular pacing wires after cardiac surgery. Using the reported search, 439 papers were found from which 13 papers represented the best evidence on the subject. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes and results are tabulated. We conclude that in 9 of the 13 papers presented, significant increases in the cardiac index and mean arterial pressure were found with biventricular pacing. In the four negative studies, which included an experimental study, the patients tended to have normal or better ejection fractions and narrow QRS complexes. Up to a 22% increase in Cardiac Index was reported in the positive studies. Exact pacing wire placement varies and some studies caution that if in the wrong place, the index can actually drop. Transoesophageal flow volume loops have been used to guide placement. Benefits seem greatest in patients with a poor ejection fraction and a wide QRS complex.

Coronary bypass grafting using crossclamp fibrillation does not result in reliable reperfusion of the myocardium when the crossclamp is intermittently released: a prospective cohort study

BackgroundCross-clamp fibrillation is a well established method of performing coronary grafting, but its clinical effect on the myocardium is unknown. We sought to measure these effects clinically using the Khuri Intramyocardial pH monitor.Methods50 episodes of cross-clamping were recorded in 16 patients who underwent CABG with crossclamp-fibrillation. An Intramyocardial pH probe measured the level of acidosis in the anterior and posterior myocardium in real-time. The pH at the start and end of each period of cross-clamping was recorded.ResultsIt became very apparent that the pH of some patients recovered quickly while others entirely failed to recover. Thus the patients were split into 2 groups according to whether the pH recovered to above 6.8 after the first crossclamp-release (N = 8 in each group). Initial pH was 7.133 (range 6.974–7.239). After the first period of crossclamping the pH dropped to 6.381 (range 6.034–6.684). The pH in recoverers prior to the second XC application was 6.990(range 6.808–7.222) compared to only 6.455 (range 6.200–6.737) in patients whose myocardium did not recover (P < 0.0005). This finding was repeated after the second XC release (mean pH 7.005 vs 6.537) and the third (mean pH 6.736 vs 6.376). However prior to separation from bypass the pH was close to the initial pH in both groups (7.062 vs 7.038).ConclusionCrossclamp fibrillation does not result in reliable reperfusion of the myocardium between periods of crossclamping.